The End of Genetics’ Golden Age

Once upon a time people believed everything associated to living things was the combination of something called “nature” and something else called “nurture”: the former, as written in the “living thing”‘s genes, and the latter, the effect of everything that was external to the “living thing”.

Whole areas of research were based on that assumption: including lots of identical-but-separated-twin studies. Since identical twins have the same genetic code, it was argued, everything that would happen to both even if they had been separated shortly after birth would clearly be caused by “nature” (i.e., the genes).

Well, we now know for sure that the above is an incorrect simplification. It’s all clear from this picture:

Those are E.coli bacteria that are genetically identical. They have even been born and lived together in the same environment.”Classical” genetics would expect them to behave identically. But they do not: having each been given extra genes to glow when digesting lactose, their colony does not glow uniformly.

As absurd as it may sound at first glance, each bacterium is a clone but also a specific individual.

It turns out that one shouldn’t just look at what genes are present in an organism, but also at the way they are “expressed“, with some of them turned on or off randomly and/or by “external forces” (“nurture” again).